Gooserider,
The bulb lies inside a quartz test tube. That way it never comes in contact with the water. In addition it does not release much heat into the water.
The overall dimensions as reported are accurate, around 3" to 3.5" inches in diameter, approx 7" long, extra inch in diameter at each hose barb.
The barbs can be easily replaced however, they are simple 1/2 inch OD NTPF threads.
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Hey CoolRod! How many fingers am I holding up??!
Do not taunt the UV Clarifier.